This project has two goals: first, to examine certain dissipative transport processes for solutes and water across lipid bilayer membranes and ways in which these processes are altered by agents such as the polyene antibiotics; and second, to apply such information to the explanation of transport processes in the isolated perfused mammalian nephron. In the bilayer we intend to describe the interactions of amphotericin B with these membranes with regard to: a) an examination of the effect of unstirred layers on ion fluxes and electrokinetic phenomena, b) the chemical nature and stoichiometry of polyene antibioticsterol interactions, and c) correlation of the permeability properties of bilayer membranes with data from isolated perfused renal tubules. Other studies with the bilayer will involve attempts to incorporate proteins and membrane active agents such as diuretics into these membranes. The second major set of investigations will be concerned with the transport of water and nonelectrolytes in the isolated perfused cortical collecting tubule. These investigations will include: a) a consideration of the effects of unstirred layers on water and solute fluxes across the tubular epithelium in the presence and absence of vasopressin, b) the effects of in vivo conditions such as chronic water loading, hypokalemia, and hypercalcemia, on the in vitro responsiveness of these tubules to vasopressin and c) an evaluation of the effects of amphotericin B on water and solute permeability of the tubules.